It says --> error:get_steps:undefined proc

How should I define this?

mob/admin
verb
Earth_Quake()
for(var/mob/M in world)
Quake_Effect(M,duration=100,strength=1)
world<<"\blue EARTHQUAKE!!!!!!!"
proc
Quake_Effect(mob/M,duration,strength=1)
if(!M.client)return
spawn(1)
var/oldeye=M.client.eye
var/x
for(x=0;x<duration,x++)
M.client.eye = get_steps(M,pick(NORTH,SOUTH,EAST,WEST),strength)
sleep(1)
M.client.eye=oldeye